In a gas turbine engine airfoil blades are secured to a turbine disk and driven by hot high pressure gas. The blades are airfoils with a neck connecting each airfoil to a root securing the blade to the disk. This root is often of the dove-tail type sliding into the disk axially or obliquely to the axis.
At the base of each airfoil and above the neck is a blade platform. In high temperature turbines this is frequently segmented with each blade being independent of the adjacent blade. The blades are therefore susceptible to vibration which can lead to a high level of repeated stress. Damping of the vibration of each blade is required to avoid these high levels of repeated stress.
The blades operate with high forces and at high temperatures, approaching the limits of the material. The blades accordingly are cooled with lower temperature air and the particular loading on the blade is a concern.
The turbines operate at high rotational&p such as 15,000 rpm which leads to a high centrifugal force in the order of 70,000 G. This produces a high load on the root and also high loading in the disk. Therefore the weight of the components secured to the disk is of concern, not only as to total engine weight but also as to the disk loading caused by the rotational forces. The high disk loading leads to larger disk and even more engine weight.
Windage losses occurring in the rotating components leads to decreased performance and heating of the cooling air. It is desirable to reduce these losses.